US6754413B2 - Optical multiplexer, demultiplexer and methods - Google Patents
Optical multiplexer, demultiplexer and methods Download PDFInfo
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- US6754413B2 US6754413B2 US10/259,597 US25959702A US6754413B2 US 6754413 B2 US6754413 B2 US 6754413B2 US 25959702 A US25959702 A US 25959702A US 6754413 B2 US6754413 B2 US 6754413B2
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- 230000003595 spectral effect Effects 0.000 claims abstract description 46
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
- G02B6/29395—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device configurable, e.g. tunable or reconfigurable
Definitions
- the invention relates to methods and apparatuses for performing multiplexing functions on groups of optical signals, and performing demultiplexing functions on multi-channel optical signals.
- the traditional solution to this problem has been to employ a wavelength specific demultiplexing device to extract the required wavelengths.
- a wavelength specific demultiplexer Referring to FIG. 1, shown is an example of such a wavelength specific demultiplexer, generally indicated by 11 .
- the input to the demultiplexer is a group of wavelengths having wavelength ⁇ 1 , . . . , ⁇ 64 .
- the demultiplexer 11 is provided which extracts those specific wavelengths and passes them to respective receivers 12 , 14 , 16 and 18 .
- the demultiplexer 11 is specifically designed for the particular wavelengths ⁇ A , ⁇ B , ⁇ C , ⁇ D which are being extracted. Typically the demultiplexer 11 and four receivers 12 , 14 , 16 and 18 might be delivered on a card 10 . In order to allow the demultiplexing of any arbitrary four wavelengths from a set of a possible 64 , it would be necessary to inventory 635 , 376 different such cards. More realistically perhaps, given the recent propensity towards grouping wavelengths into bands of consecutive wavelengths, in order to allow the demultiplexing of any consecutive group of four wavelengths in a 64 wavelength system, for example ⁇ 1 , . . . ⁇ 4 ⁇ , ⁇ 5 , . . . ⁇ 8 ⁇ , . . . , ⁇ 61 , . . . , ⁇ 64 ⁇ there would be a requirement to inventory 16 different demultiplexer cards.
- Methods and devices are provided for optical demultiplexing and optical multiplexing.
- One broad aspect of the invention provides an optical wavelength demultiplexer adapted to perform wavelength demultiplexing of an input optical signal containing a plurality of wavelengths.
- the demultiplexer has a wavelength selective element adapted to act upon the input optical signal to produce an output containing a selected subset of the plurality of wavelengths, and as a band-modulo demultiplexer having a free spectral range, the band-modulo demultiplexer being connected to receive the output of the wavelength selective element.
- the wavelength selective element is adapted to produce the output containing the selected subset consisting of an arbitrary subset of wavelengths from the plurality of wavelengths.
- the wavelength selective element is adapted to produce the output containing the selected subset consisting of an arbitrary subset of wavelengths from the plurality of wavelengths subject to a constraint that no two wavelengths in the arbitrary subset are separated by a multiple of the free spectral range.
- the wavelength selective element is adapted to select a contiguous set of wavelengths
- the wavelength selective element is a bandpass filter having a passband.
- the wavelength selective element comprises a bank of components which are individually selectable, each component being adapted to select a respective contiguous set of wavelengths.
- each component is a bandpass filter having a passband.
- a guardband is provided between sets of contiguous wavelengths, and the FSR is substantially equal to a width of the contiguous set of wavelengths plus the guardband.
- Another broad aspect of the invention provides an optical wavelength demultiplexer adapted to perform wavelength demultiplexing of an input optical signal containing a plurality of wavelengths.
- the demultiplexer has a band-modulo demultiplexer having a free spectral range, the band-modulo demultiplexer being connected to receive the input optical signal, and adapted to act upon the input optical signal to produce a plurality of intermediate output signals each containing one or more of the plurality of wavelengths each separated by the free spectral range.
- each wavelength selective device comprises at least one component adapted to pass a contiguous band of wavelengths.
- the component is a bandpass filter.
- the wavelength selective devices comprise a plurality of static bandpass filters which are individually selectable, each bandpass filter having a passband width substantially equal to the free spectral range of the band-modulo demultiplexer.
- the wavelength selective devices comprise a plurality of static bandpass filters which are individually selectable, with a guardband being defined between a passband of each bandpass filter, such that for each filter, the guardband plus passband width is substantially equal to the free spectral range of the band-modulo demultiplexer.
- each wavelength selective device comprises a tuneable bandpass filter having a passband width less than the free spectral range of the band-modulo demultiplexer thereby allowing a guard band between bands of wavelengths.
- each wavelength selective element is adapted to filter an arbitrary subset of wavelengths from the plurality of wavelengths subject to a constraint that no two wavelengths are separated by a multiple of the free spectral range.
- Another broad aspect of the invention provides an optical wavelength demultiplexer adapted to perform wavelength demultiplexing of an input optical signal containing a plurality of wavelengths.
- the demultiplexer has a fixed wavelength selective element adapted to act upon the input optical signal to produce an output containing a selected subset of the plurality of wavelengths and has a band-modulo demultiplexer having a free spectral range, the band-modulo demultiplexer being connected to receive the output of the wavelength selective element.
- the demultiplexer has a wavelength selective element adapted to act upon the input optical signal to produce an output containing a selected subset of the plurality of wavelengths, the wavelength selective element comprising a plurality of components each adapted to select a respective subset of the plurality of wavelengths, and switching circuitry for selecting one of the plurality of components to be active at a given time; and a band-modulo demultiplexer having a free spectral range, the band-modulo demultiplexer being connected to receive the output of the wavelength selective element.
- Another broad aspect of the invention provides an optical wavelength demultiplexer adapted to perform wavelength demultiplexing of an input optical signal containing a plurality of wavelengths.
- the multiplexer has a tuneable wavelength selective element adapted to act upon the input optical signal to produce an output containing a selected subset of the plurality of wavelengths; a band-modulo demultiplexer having a free spectral range, the band-modulo demultiplexer being connected to receive the output of the wavelength selective element.
- the multiplexer has a band-modulo multiplexer having a free spectral range, the band-modulo multiplexer having a plurality of inputs with one input for each of the plurality of input optical signals, the band-modulo multiplexer producing a multiplexed output signal, the band-modulo multiplexer being adapted to combine as the multiplexed output signal for each input any input optical wavelengths in a respective predetermined set of possible wavelengths, each possible wavelength in the set being separated by the free spectral range.
- FIG. 1 is a block diagram of a conventional multi-wavelength demultiplexer
- FIG. 2 is a block diagram of an optical demultiplexer provided by an embodiment of the invention.
- FIG. 3 is a schematic diagram of the band-modulo demultiplexer of FIG. 2;
- FIG. 4 is a block diagram of an optical demultiplexer according to another embodiment of the invention.
- FIG. 5 is a schematic diagram of an interleaver based band-modulo demultiplexer provided by another embodiment of the invention.
- FIG. 6 is a schematic diagram of an optical multiplexer provided by another embodiment of the invention.
- FIG. 7 is a schematic diagram of an optical network provided by another embodiment of the invention.
- FIG. 8 is a flowchart of a method of wavelength planning, provided by another embodiment of the invention.
- FIG. 9 is a block diagram of an optical demultiplexer provided by an embodiment of the invention.
- FIG. 10 is a block diagram of an optical demultiplexer according to another embodiment of the invention.
- the demultiplexer has an input optical transmission medium 20 adapted to contain a multi-band optical signal containing multiple wavelengths, ⁇ 1 , . . . , ⁇ N .
- the input optical transmission medium is connected to a tuneable bandpass filter 22 , the output 24 of which is connected to a band-modulo demultiplexer 26 .
- the tuneable bandpass filter 22 has a passband equal in width to the bands of wavelengths, and is tuneable such that it can be centered to have a passband which overlaps with any particular one of the K bands B 1 , . . . B K .
- the output 24 of the tuneable band pass filter 22 once tuned, consists of the wavelengths in a selected band B i only. This output is connected to the band-modulo demultiplexer 26 which separates the wavelengths of the band B i selected by the tuneable bandpass filter 22 into outputs 28 which are individual substituent wavelengths of the band B i .
- the band-modulo demultiplexer 26 is a device which takes as input a spectrum of wavelengths, preferably with constant channel spacing in frequency, and outputs to more than two ports such that each port outputs a different group of wavelengths that are separated by the FSR (free spectral range) of the device.
- the free spectral range of the device is the range of wavelengths in a given spectral order for which superposition of light from adjacent orders does not occur.
- Output 1 ⁇ 1 , ⁇ M+1 , ⁇ 2M+1 , . . . , ⁇ (K ⁇ 1)M+1 .
- Output 2 ⁇ 2 , ⁇ M+2 , ⁇ 2M+2 , . . . , ⁇ (K ⁇ 1)M+2 .
- Output 3 ⁇ 3 , ⁇ M+3 , ⁇ 2M+3 , . . . , ⁇ (K ⁇ 1)M+3 .
- Output M ⁇ M , ⁇ 2M , ⁇ 3M , . . . , ⁇ KM .
- the FSR is set to equal the frequency spacing between corresponding wavelengths in each band. Using the above notation, the FSR will be set to equal the frequency of ⁇ M+1 minus the frequency of ⁇ 1 for example. In one embodiment, each of the N wavelengths are equally spaced in frequency.
- the bands each contain M equally spaced frequencies, but a guard band is provided between bands.
- the bands each contain M frequencies which are not equally spaced, but with the spacing of the frequencies within a given band being equal across bands.
- Guard bands can also be employed in this embodiment.
- the tuneable band pass filter 22 serves to eliminate all of the wavelengths being input to the band-modulo demultiplexer 26 except the M wavelengths of a single band B i .
- the arrangement of FIG. 2 can be mass-produced, and tuning the arrangement to produce a demultiplexer function specific to a particular band B i simply involves tuning the tuneable band pass filter 22 to pass the particular band.
- the band-modulo demultiplexer 26 of FIG. 3 is connected to receive an input optical signal 30 containing the wavelengths ⁇ 1 , . . . , ⁇ N so as to produce M outputs containing multiple wavelengths as described above.
- Each output is connected to a respective tuneable channel filter 40 (only two shown) which is tuneable to pass one or more of the multiple wavelengths it receives.
- the first of the outputs 32 contains the “first” wavelength of each band B 1 , . . . , B K .
- the tuneable channel filter 40 receiving that output can be tuned to extract any particular first wavelength.
- the input set of wavelengths ⁇ 1 , . . . , ⁇ N ⁇ is in the lower C band (194.15 to 196.1 THz) with 50 GHz spacing between wavelength frequencies, with the longest and shortest wavelengths in a given band B i differing in frequency by 350 GHz. This results in 5 bands B i each containing 8 wavelengths for a total of 40 wavelengths.
- the input set of wavelengths ⁇ 1 , . . . , ⁇ N ⁇ is in the upper C band (192.1 to 194.1 THz) with 50 GHz spacing between wavelength frequencies, with the longest and shortest wavelengths in a given band B i differing in frequency by 400 GHz. This results in 5 bands B i each containing 8 wavelengths for a total of 40 wavelengths.
- the band-modulo demultiplexer 26 may be implemented using any suitable “FSR device”, this being any optical element or combination of elements which exhibit the required FSR.
- the band-modulo demultiplexer is a grating based structure, and preferably an Echelle grating based structure.
- Echelle gratings are available for example from Metro Photonics Inc. of Ottawa, Canada.
- the FSR has been thought of as a limitation of the usefulness of Eshelle gratings.
- the FSR is substantially equal to the bandpass width of the tuneable bandpass filter.
- the FSR is smaller than the bandpass width of the tuneable bandpass filter in which case each output may have more than one wavelength. For example, having the FSR equal to one half the bandpass width of the tuneable bandpass filter will result in each output of the arrangement containing two wavelengths separated by the FSR.
- the FSR is broader than the passband width of the tuneable bandpass filter. This will result in gaps in the set of wavelengths which are demultiplexible by the arrangement. This can be employed to provide a guard band of one or more wavelengths between bands of interest.
- the band-modulo demultiplexer 26 of FIGS. 2 and 3 is an interleaver-based structure.
- the input optical signal potentially having any of 64 possible wavelengths ⁇ 1 , . . . , ⁇ 64 ⁇ is fed to a first interleaver 52 which separates the wavelengths into an output 54 carrying the odd wavelengths ⁇ 1 , ⁇ 3 , . . . , ⁇ 63 ⁇ and an output 56 carrying the even wavelengths ⁇ 2 , ⁇ 4 , . . .
- interleavers 60 , 62 The two outputs 54 , 56 are connected to respective interleavers 60 , 62 .
- Interleaver 60 further interleaves the odd wavelengths to produce output 64 carrying ⁇ 1 , ⁇ 5 , . . . , ⁇ 61 ⁇ and output 66 carrying ⁇ 3 , ⁇ 7 , . . . , ⁇ 63 ⁇ .
- interleaver 62 further interleaves the even wavelengths to produce output 68 carrying ⁇ 2 , ⁇ 6 , . . . , ⁇ 62 ⁇ and output 69 carrying ⁇ 4 , ⁇ 8 , . . . , ⁇ 64 ⁇ .
- the multiplexer has a band-modulo multiplexer 74 which is essentially the reciprocal function of the previously discussed band-modulo demultiplexer.
- the band-modulo multiplexer 74 takes a group of wavelengths that are separated from each other by the free spectral range into more than two ports 72 such that each port intakes a different group of wavelengths. More specifically, the inputs are capable of multiplexing the following wavelengths:
- Input 1 any combination of ⁇ 1 , ⁇ M+1 , ⁇ 2M+1 , . . . , ⁇ (K ⁇ 1)M+3 .
- Input 2 any combination of ⁇ 2 , ⁇ M+2 , ⁇ 2M+2 , . . . , ⁇ (K ⁇ 1)M+2 .
- Input 3 any combination of ⁇ 3 , ⁇ M+3 , ⁇ 2M+3 , . . . , ⁇ (K ⁇ 1)M+3 .
- Input M any combination of ⁇ M , ⁇ 2M , ⁇ 3M , . . . , ⁇ KM .
- Wavelengths input to the wrong port are attenuated and lost.
- the band-modulo multiplexer 74 outputs at output 76 all the input wavelengths in wavelength order.
- a tuneable laser 70 may be applied to any one of the input ports 72 with one of the multiple wavelengths available at the port. For example, on the second input port, one can transmit the second wavelength for any of one of the supported bands.
- the output of the wavelengths produced at output 76 may not all fall in the same band depending on the input wavelengths.
- Another embodiment provides an optical wavelength multiplexer adapted to perform wavelength multiplexing of a plurality of input optical signals each containing a plurality of wavelengths.
- the multiplexer has a band-modulo multiplexer having a free spectral range, the band-modulo multiplexer having a plurality of inputs with one input for each of the plurality of input optical signals, the band-modulo multiplexer producing a multiplexed output signal, the band-modulo multiplexer being adapted to combine as the multiplexed output signal for each input any input optical wavelengths in a respective predetermined set of possible wavelengths, each possible wavelength in the set being separated by the free spectral range.
- FIG. 7 shown is an example network provided by this embodiment of the invention which a number of ONNs (optical network nodes) 100 , 102 , 104 (only three shown) interconnected by optical network links 106 , 108 , 110 .
- ONNs optical network nodes
- One or both of the previously described optical multiplexer and optical demultiplexer is installed in each of the optical network nodes 100 , 102 , 104 , generally indicated as multiplexer/demultiplexer (mux/demux) 112 , 114 , 116 .
- Such an optical network is flexible in that the particular wavelengths to be added and/or dropped by each node can be selected by appropriate tuning of either the multiplexer and/or the demultiplexer.
- the method involves first providing each of at least two optical network nodes with either or both of the above described multiplexer and demultiplexer capability using a tuneable multiplexer, and/or a tuneable demultiplexer (step 8 - 1 ). Preferably, this is done in each of the optical network nodes in an optical network. Next, after determining desired wavelengths to be added and/or dropped at each of the optical network nodes, each the filters in each multiplexer and/or demultiplexer are tuned so that the desired wavelengths are added and/or dropped at each optical network node (step 8 - 2 ).
- the step of tuning the multiplexer and/or demultiplexer may be done prior to network interconnection, or after network interconnection, and advantageously may be optionally repeated when the wavelength plan for the network is changed for any reason (step 8 - 3 ).
- a demultiplexer which has a wavelength selective element, such as a tuneable filter, which is adapted to filter the input optical signal to produce an output containing a selected subset of the plurality of wavelengths.
- the selected subset is one of a number of contiguous bands of wavelengths as exemplified above.
- the wavelength selective element is adapted to produce a selected subset which is a completely arbitrary set.
- the selected subset does not include any wavelengths separated by multiples of the FSR of the FSR device as this would result in collision.
- the first wavelength of the first band, the second wavelength of the third band, the fourth wavelength of the third band, and the third wavelength of a fourth band could be filtered and demultiplexed successfully without collision.
- the wavelength selective element is implemented with a bank of wavelength selective components, such as bandpass filters for example, each passing a respective band, and a switch to select between the components.
- a bank of wavelength selective components such as bandpass filters for example, each passing a respective band, and a switch to select between the components.
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Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/259,597 US6754413B2 (en) | 2001-04-23 | 2002-09-30 | Optical multiplexer, demultiplexer and methods |
US10/612,908 US6912340B2 (en) | 2001-04-23 | 2003-07-07 | Optical ring interconnect |
CA 2434723 CA2434723A1 (en) | 2002-09-30 | 2003-07-07 | Optical multiplexer, demultiplexer and methods |
CA 2434729 CA2434729A1 (en) | 2002-08-14 | 2003-07-07 | Optical ring interconnect |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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US09/839,487 US20020154856A1 (en) | 2001-04-23 | 2001-04-23 | Optical multiplexer, demultiplexer and methods |
US10/259,597 US6754413B2 (en) | 2001-04-23 | 2002-09-30 | Optical multiplexer, demultiplexer and methods |
Related Parent Applications (1)
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US09/839,487 Continuation-In-Part US20020154856A1 (en) | 2001-04-23 | 2001-04-23 | Optical multiplexer, demultiplexer and methods |
Related Child Applications (1)
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US10/612,908 Continuation-In-Part US6912340B2 (en) | 2001-04-23 | 2003-07-07 | Optical ring interconnect |
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US20030026530A1 US20030026530A1 (en) | 2003-02-06 |
US6754413B2 true US6754413B2 (en) | 2004-06-22 |
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US10/259,597 Expired - Lifetime US6754413B2 (en) | 2001-04-23 | 2002-09-30 | Optical multiplexer, demultiplexer and methods |
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Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20050213886A1 (en) * | 2004-03-24 | 2005-09-29 | Ashok Balakrishnan | Double diffraction grating with flat passband output |
US20090047019A1 (en) * | 2007-08-13 | 2009-02-19 | Paparao Palacharla | Method and System for Communicating Optical Traffic |
US20160164625A1 (en) * | 2013-07-16 | 2016-06-09 | Commscope Technologies Llc | Distributed wave division multiplexing systems |
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US5461685A (en) * | 1993-10-18 | 1995-10-24 | At&T Ipm Corp. | Optical passband filter |
US5491582A (en) * | 1991-08-29 | 1996-02-13 | Nec Corporation | Light-receiving module |
US5680490A (en) * | 1995-09-08 | 1997-10-21 | Lucent Technologies Inc. | Comb splitting system and method for a multichannel optical fiber communication network |
US20020012144A1 (en) * | 1998-08-31 | 2002-01-31 | Wenhua Lin | Scalable optical demultiplexing arrangement for wide band dense wavelength division multiplexed systems |
US20020131689A1 (en) * | 2001-03-19 | 2002-09-19 | At&T Corporation | Four-port wavelength-selective crossbar switches (4WCS) using reciprocal WDM MUX-DEMUX and optical circulator combination |
-
2002
- 2002-09-30 US US10/259,597 patent/US6754413B2/en not_active Expired - Lifetime
Patent Citations (5)
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US5491582A (en) * | 1991-08-29 | 1996-02-13 | Nec Corporation | Light-receiving module |
US5461685A (en) * | 1993-10-18 | 1995-10-24 | At&T Ipm Corp. | Optical passband filter |
US5680490A (en) * | 1995-09-08 | 1997-10-21 | Lucent Technologies Inc. | Comb splitting system and method for a multichannel optical fiber communication network |
US20020012144A1 (en) * | 1998-08-31 | 2002-01-31 | Wenhua Lin | Scalable optical demultiplexing arrangement for wide band dense wavelength division multiplexed systems |
US20020131689A1 (en) * | 2001-03-19 | 2002-09-19 | At&T Corporation | Four-port wavelength-selective crossbar switches (4WCS) using reciprocal WDM MUX-DEMUX and optical circulator combination |
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"BMX™ Series", Preliminary Specifications, Feb. 2001, 2001 MetroPhotonics Inc., pp. 1 to 4. |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20050213886A1 (en) * | 2004-03-24 | 2005-09-29 | Ashok Balakrishnan | Double diffraction grating with flat passband output |
US7149387B2 (en) * | 2004-03-24 | 2006-12-12 | Enablence Inc. | Double diffraction grating with flat passband output |
US20090047019A1 (en) * | 2007-08-13 | 2009-02-19 | Paparao Palacharla | Method and System for Communicating Optical Traffic |
US20160164625A1 (en) * | 2013-07-16 | 2016-06-09 | Commscope Technologies Llc | Distributed wave division multiplexing systems |
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US20030026530A1 (en) | 2003-02-06 |
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